Swallowing dysfunctions in patients with disorders of consciousness

What is it about?

Following severe brain injuries, a subset of patients may exhibit disorders of consciousness. In the most severe cases, these patients only show reflexive behaviors while others may also show voluntary behaviors such as visual pursuit or command following. Most patients with such disorders of consciousness experience severe dysphagia (i.e., swallowing disorders) requiring artificial nutrition. However, these complications remain poorly documented at present, and their characteristics are not well understood. To gain a deeper understanding of swallowing disorders in patients with disorders of consciousness, it is worthwhile to explore the relationship between consciousness and swallowing. In this literature review, we describe the different phases of swallowing and question their voluntary or reflexive nature. Subsequently, based on observations of patients with disorders of consciousness, we describe swallowing elements that are associated with the level of consciousness or appear to be indicative of consciousness. Additionally, we review studies that have analyzed cerebral activation during tasks of "voluntary" swallowing and compare them with studies exploring "non-voluntary" tasks. Finally, this review also outlines suitable assessment and treatment methods for dysphagic patients with disorders of consciousness.

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Photo by Annie Spratt on Unsplash

Photo by Annie Spratt on Unsplash

Why is it important?

A better understanding of the links between consciousness and swallowing may enhance the assessment and management of dysphagia in severe brain-injured patients with disorders of consciousness. Furthermore, the clinical observations regarding swallowing are currently not considered for the diagnosis of the patients' level of consciousness. However, several swallowing elements appear to be indicative of consciousness, such as mouth opening upon approach of a spoon, lip closure and bolus propulsion with the tongue, and the ability to exclusively feed orally. Therefore, it is crucial to further characterize the swallowing disorders in these patients not only to improve their management but also to contribute to the diagnostic criteria for patients' level of consciousness.